Evolution and functional diversity of abiotic stress-responsive NAC transcription factor genes in Linum usitatissimum L

Global cultivation of flax fibre and oilseed is sparse due to poor climatic adaptability. Abiotic stresses, such as drought, salinity, and heat stress are the major limiting factors of flax cultivation. Varieties tolerant to biotic and abiotic stresses are the need of the hour with a sustainable high and stable yield. Exploring candidate genes to provide wider climatic adaptability in flax is of paramount importance. The present study delineates a detailed annotation of 164 Linum usitatissimum NAC-domain transcription factor genes (LuNACs) that are scattered across all 15 chromosomes. Phylogeny-wise majority of the LuNAC proteins were categorized into recognized NAC groups. Few LuNACs remain distinct, suggesting their species-specific expansion. Analysis of the LuNAC gene and protein domain architectures established their conserved nature and support the phylogenetic grouping. The homologs of LuNAC genes revealed their expansion because of whole-genome duplication events. Potential target sites of miRNA families, including the miRNA164, were identified in LuNAC genes, suggesting that a complex regulatory mechanism might be associated with abiotic stress tolerance in flax. In silico gene expression, deep GO analysis, functional inference from homologs, and RT-qPCR of selected LuNAC genes revealed their functional involvement in growth and development and in response to diverse abiotic stresses in flax. The LuNAC003 gene from the senescence-related subfamily was responsive to multiple stress conditions. All the above findings on LuNAC genes may promote them as candidate genes for further functional studies or utilize them in flax genetic improvement programs for improved fibre and seed oil productions, even under adverse environmental conditions.